Events next week in Rio and other Brazilian cities linked to the COP30 climate summit will be safe for visitors, a Brazilian ministry official said, seeking to reassure attendees after a bloody police crackdown on a drug gang that led to dozens of deaths.

The deadliest police operation in Brazil’s history killed at least 132 people, public defenders said on Wednesday. Grisly images showed a favela street lined with corpses found overnight by local residents.

UN Secretary-General Antonio Guterres, who will join Brazilian officials in presiding over next month’s summit, urged Brazil to mount a prompt investigation and to ensure any police action followed international human rights law and standards, his spokesman said.

“I can tell you that the secretary-general is gravely concerned by the large number of casualties during a police operation conducted yesterday in the favelas in Rio de Janeiro,” spokesman Stephane Dujarric said.

Rio’s mayor and governor have insisted that the violence was part of a crackdown on crime and had nothing to do with the summit events being staged across three cities – Rio, Sao Paulo and the coastal Amazon city of Belem. Brazilian police held a security drill in Belem on Tuesday.

In comments to Reuters, a finance ministry official said COP30 events would be safe for the tens of thousands expected to attend from around the world.

“I would say it’s a very localized thing; it has nothing to do with the climate agenda or the COP itself,” said Joao Paulo de Resende, the ministry’s undersecretary for economic and fiscal affairs.

“It’s very unusual (even) by Brazilian standards, what happened yesterday. It’s not something that you’re probably going to see repeating itself in the next couple of weeks or months.”

The US consulate issued a travel warning for affected Rio neighbourhoods, citing “ongoing fighting between police and criminal factions.”

COP30 attendees speaking with Reuters on Wednesday said they were undaunted. Rio is set to host a climate summit for local leaders next week, along with Prince William’s Earthshot Prize. Business and banking officials will be meeting in Sao Paulo to discuss climate finance, while world leaders gather in Belem ahead of COP30 negotiations later in November.

“From our side, nothing has changed; I’m not aware of any businesses reconsidering their plans. We know it’s going to be logistically challenging but certainly nothing has changed in the last 24 hours,” said Andrew Wilson, deputy secretary-general of the International Chamber of Commerce.